No such rule appears to exist.

I can't personally track down any rule which covers this particular question - but then again, I would not expect to be able to. The extent to which the DM, and even the other players, can describe how the other characters feel is something that has to be agreed (implicitly or otherwise) by the group.

Personally, I do strongly prefer complete player autonomy as you do; I wouldn't presume to tell my players how their characters feel about a particular situation, except insofar as the game rules sometimes dictate that they are subject to certain emotional conditions, like an enraged barbarian, or a character with the Frightened condition. Likewise I would be a little affronted if my DM started telling me, as a player, how my character feels about something, as opposed to what my character knows and sees.

However, I have the impression it is somewhat more common with players who are used to roleplaying in play-by-post forum environments that, due to the nature of the medium they're used to (you can't expect real-time responses in play-by-post games), they tend to assume a bit more leeway in narrating how other characters might be responding to whatever they are doing.

Regardless of the source this could be a difficult habit to break; maybe it will help you if you consider your friend's narration as a suggestion, rather than a statement of fact, and respond as if so:

"You feel a tear beginning to well up in your eye as you consider this poor orphan's plight..."

 

"Nah, Urist Grimdark hates children. They're only good for fetching ale and mining in the smaller shafts."

If this dynamic works for you to preserve your character autonomy, then you've solved the problem, and you might find that your friend breaks himself of the habit of dictating how you feel if you routinely gently correct his presumptions.

No such rule appears to exist.

I can't personally track down any rule which covers this particular question - but then again, I would not expect to be able to. The extent to which the DM, and even the other players, can describe how the other characters feel is something that has to be agreed (implicitly or otherwise) by the group.

Personally, I do strongly prefer complete player autonomy as you do; I wouldn't presume to tell my players how their characters feel about a particular situation, except insofar as the game rules sometimes dictate that they are subject to certain emotional conditions, like an enraged barbarian, or a character with the Frightened condition. Likewise I would be a little affronted if my DM started telling me, as a player, how my character feels about something, as opposed to what my character knows and sees.

However, I have the impression it is somewhat more common with players who are used to roleplaying in play-by-post forum environments that, due to the nature of the medium they're used to (you can't expect real-time responses in play-by-post games), they tend to assume a bit more leeway in narrating how other characters might be responding to whatever they are doing.

Regardless of the source this could be a difficult habit to break; maybe it will help you if you consider your friend's narration as a suggestion, rather than a statement of fact, and respond as if so:

"You feel a tear beginning to well up in your eye as you consider this poor orphan's plight..."

"Nah, Urist Grimdark hates children. They're only good for fetching ale and mining in the smaller shafts."

If this dynamic works for you to preserve your character autonomy, then you've solved the problem, and you might find that your friend breaks himself of the habit of dictating how you feel if you routinely gently correct his presumptions.